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Andrew Morton wrote: > Christian Leber <christian@leber.de> wrote: > [...] >>+ for (pb = 0; prop0 >= (9 * 5); pb++, prop0 -= (9 * 5)); >>+ for (lp = 0; prop0 >= 9; lp++, prop0 -= 9); > > Put the ";" on a line of its own. > > I'd have thought the above could be done arithmetically? I just tried a small test program to see the speed/code size difference to this code, which is the arithmetic equivalent: pb = prop0 / (9 * 5); prop0 %= (9 * 5); lp = prop0 / 9; prop0 %= 9; This code runs a lot faster than the original. This is not very important since it runs only once AFAICT. As for the code size, it is smaller if compiled with -Os, but larger when compiled with -O2 or -O3. When compiled with -Os, gcc uses the idiv instruction and it even uses its reminder so that it only does 2 idiv instructions to do the 4 operations above. With -O2 or -O3, it does a hard to follow division "by hand" using several instructions, rendering the code about 2.5x larger (but amazingly a lot faster). The tests were done with gcc 3.3.2. -- Paulo Marques - www.grupopie.com An expert is a person who has made all the mistakes that can be made in a very narrow field. Niels Bohr (1885 - 1962) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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